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The Air Force on Wednesday named the 12th military training instructor at Joint Base San Antonio-Lackland charged with improper contact with trainees since a scandal emerged there in the summer of 2011.

Staff Sgt. Ryan J. Derass is accused of having unprofessional relationships with five technical training students, willful dereliction of duty, maltraining and assault and battery on two trainees, a base news release said.

Maltraining can include abusive and excessive physical training.

Derass will face an Article 32, or preliminary, hearing Dec. 10, to determine whether there is enough evidence to send his case to court-martial.

The Air Force announced in November that it had charged a dozen MTIs in the ongoing scandal, but until this week had named only 10 of them.

Tech. Sgt. Samuel Wicks, also named this week, is scheduled for an Article 32 hearing Thursday. Wicks is accused of having unprofessional relationships with three students in technical training, indecent conduct and obstruction of justice.

Allegations in the dozen cases have ranged from rape to contact with trainees over social media. In the most serious case, ex-Staff Sgt. Luis Walker was accused of sexually assaulting multiple trainees. Walker is serving a 20-year prison sentence for his crimes.